Hello,
Thanks for the great question. That spacing is actually baked into the theme itself.
There are two separate styles that control the spacing at the top of your entry content. In order to reduce these, navigate to your Customize > Advanced > Custom JS & CSS menu, and paste the following snippet into your Custom Theme CSS:
.entry-content { padding-top: 0px !important; }
That will reduce the space from 6.5em to 1.5em. If you want to eliminate all of the space, use this CSS:
.entry-content {
padding-top: 0px !important;
margin-top: 0px !important;
}
I hope this helps!